SPACECRAFT ACCIDENTS: EXAMINING THE PAST, IMPROVING THE FUTURE Mars Climate Orbiter MCO and Mars Pol

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SPACECRAFT ACCIDENTS EXAMINING THE PAST,
IMPROVING THE FUTUREMars Climate Orbiter (MCO)
and Mars Polar Lander (MPL)

• Bryan Palaszewski
• working with the
• Digital Learning Network
• NASA Glenn Research Center

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Mars Climate Orbiter (1/2)

• Launched from Earth
• December 11, 1998
• Payload on spacecraft
• Camera and other sensing instruments
  investigating the atmosphere and possible
  subsurface ices

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Mars Climate Orbiter (2/2)

• Payload on spacecraft (continued)
• Similar to but smaller payload than Mars Observer
  that was lost in 1993
• Arrival at Mars
• September 23, 1999
• Planned to use rocket engine to slow into Mars
  orbit

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MCO Root Cause

• Failure to use metric units in the coding of a
  ground software file, Small Forces, used in
  trajectory models

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MCO Contributing Causes (1/2)

• Undetected mis-modeling of spacecraft velocity
  changes
• Navigation Team unfamiliar with spacecraft
• Trajectory correction maneuver number 5 not
  performed
• System engineering process did not adequately
  address transition from development to operations.

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MCO Contributing Causes (2/2)

• Inadequate communications between project
  elements
• Inadequate operations Navigation Team staffing
• Inadequate training
• Verification and validation process did not
  adequately address ground software.

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MCO Recommendations (1/3)

• Verify the consistent use of units throughout the
  MPL spacecraft design and operations.
• Conduct software audit for specification
  compliance on all data transferred between JPL
  and Lockheed Martin Astronautics.
• Verify Small Forces models used for MPL.

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MCO Recommendations (2/3)

• Compare prime MPL navigation projections with
  projections by alternate navigation methods.
• Train Navigation Team in spacecraft design and
  operations.
• Prepare for possibility of executing trajectory
  correction maneuver number 5.

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MCO Recommendations (3/3)

• Establish MPL systems organization to concentrate
  on trajectory correction maneuver number 5 and
  entry, descent, and landing operations.
• Take steps to improve communications.

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Mars Polar Lander (1/2)

• Launched from Earth
• January 3, 1999
• Payload on spacecraft
• Camera and other sensing instruments looking for
  volatiles (water, etc.) and investigating the
  climate at the Martian South Pole

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Mars Polar Lander (2/2)

• Arrival at Mars
• December 3, 1999
• Planned to use Mars atmosphere for initial
  braking and then rocket engines for the final
  landing on Mars.

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MPL Findings Most Probable Cause Of Loss Of
Mission (1/3)

• Premature shutdown of descent engines
• The software intended to ignore touchdown
  indications prior to the enabling of the
  touchdown sensing logic was not properly
  implemented, and the false touchdown indication
  was retained.

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MPL Findings Most Probable Cause Of Loss Of
Mission (2/3)

• The touchdown sensing logic was enabled at 40
  meters altitude, and the software would have
  issued a descent engine thrust termination at
  this time in response to a (false) touchdown
  indication.

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MPL Findings Most Probable Cause Of Loss Of
Mission (3/3)

• At 40 meters altitude, the lander had a velocity
  of about 13 meters per second (m/s), which with
  no thrust is accelerated by Mars gravity to an
  impact velocity of about 22 m/s.
• The planned touchdown velocity was 2.4 m/s.
• At this impact velocity, the lander could not
  have survived.

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MPL Findings (1/2)

• The flight software was not subjected to complete
  fault-injection testing.
• Problems with post-landing fault-response
  algorithms were uncovered in the course of the
  investigation.
• The touchdown sensing software was not tested
  with the lander in the flight configuration.

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MPL Findings (2/2)

• Because of this, the software error was not
  discovered during the verification and validation
  program.

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